Amine-containing materials, such as amine-containing analytes, amino acids, DNA fragments, RNA fragments, protein fragments, organelles, and immunoglobins, immobilized on the surface of a substrate can be used in numerous applications. The covalent attachment of amine-containing materials to a substrate can be accomplished, for example, by the reaction of the amine with a reactive group on the surface of the substrate. This amine-reactive functional group can be, for example, an activated acyl derivative, such as an N-hydroxysuccinimide ester; or, an active cyclic acyl compound, such as azlactone. A stable amide bond is formed from reaction of the amine with the active acyl group, either with expulsion of N-hydroxysuccinimide or ring opening of the azlactone.
Amine-reactive functional groups have been attached to substrates by specific functional group reactions with complementary substrate chemistry and by deposition of soluble polymers comprising the amine-reactive functional groups. Deposition of polymers has advantages over reactive functional groups for some substrates. Polymeric films can have adequate physical adhesion to a variety of inorganic and organic substrates without specific complementary functional groups on the substrate surface. The mechanical properties of polymeric films, such as Tg, can be designed for specific requirements by selection of the type of polymer and comonomers.
Although functional groups such as N-hydroxysuccinimide esters and azlactone are highly reactive with amines, they can suffer from a number of disadvantages. Many of the reactions with biological amines are conducted in dilute aqueous solutions, conditions known to cause rapid hydrolysis of N-hydroxysuccinimide esters. This competing reaction can result in incomplete or inefficient immobilization of the amine-containing materials onto the substrate.
A solution to this problem has been to use polymeric coatings based on polymers made from vinylazlactones. However, the azlactone group is synthetically incompatible with many functional groups that can be used to link it to a polymerizable vinyl group, and it is therefore most often incorporated using vinylazlactone monomers. This monomer readily polymerizes or co-polymerizes with a variety of vinyl monomers to provide solutions of polymers having pendant amine reactive azlactone substituents bonded directly to the polymeric backbone. These solutions can be coated onto substrates to obtain amine-reactive surfaces.
Thus, there exists a need for soluble polymeric materials with alternative amine reactive functional groups that can be used as coatings for the activation of surfaces for the immobilization of amine-containing materials.